The present invention relates to a process for the production of veneer and more particularly to a process for producing sheets of wide veneer to be applied to plywood and sheets of wide, thin veneer for producing fancy board (veneer-overlaid board) in one operational step.
In conventional processes for producing sliced wood veneer to be glued on a substrate or to be used for plywood, a log is longitudinally and transversely sawn into various-sized small flitches and they are subsequently sliced individually by means of a slicer or a rotary lathe into sheets of thin veneer. In this case, such small individual flitches in green condition can be sliced as they are, but when they are dry, they must be steamed or cooked for a long time before being sliced. The sheets of thinly sliced veneer thus produced are cut to have a suitable width by a guillotine or the like. And before gluing the sliced veneer onto a substrate, it is usual to dry and to correct unevenness on the surfaces of the sheets of veneer and to remove oil remaining thereon in the step of dividing and to effect a trimming and sorting into different lots having desired wood pattern.
According to this known process, however, the core timber f and triangular sections e of the logs (FIG. 1) wind up as scrap without being used in the sliced sheets of veneer. In addition, the sides of the wood, as mentioned above, are cut off and are unavailablly, so in other words, only about 40% of the original log can be really used as a material for veneer in spite of the great value of lumber. And more than that, those processes require drying and cooking or steaming which consume a great deal of fuel and electricity.
In addition, sliced sections of veneer are required to be patched onto the substrate or the veneer and have to be cut one by one by hand in a known method and to overlap or fill in the gap in the sheets of veneer. The patching step is also effected by hand. Under present conditions of such manufacture, it can be said that 80% of the labor required throughout the process must be assigned to this patching and mending work. Such inefficiency in conventional manufacturing processes makes it necessary to store the sliced veneers which are not used under severly controlled conditions to keep them from transforming, falling into decay, or getting moldy due to changes of moisture content.
On the other hand, such process of producing veneer from laminated wood has been employed in only a small percentage, that is only 1 to 2% of the total production of veneer. It also requires steps comprising sawing a log into flitches, drying, laminating the flitch by gluing, cooking (or steaming) and slicing the laminated flitch into sheets of veneer, and gluing each sheet onto a board. Furthermore, the flitch employed in the process is limited in size to less than 100 mm in thickness due to the following reasons:
1. A large flitch, e.g. 300 mm in thickness requires several days to some dozen days even by drying in a drier at a factory.
2. The adhering surfaces of a larger flitch cannot be smoothed by means of plane so as to be fitted overall the surface perfectly.
3. A larger flitch is apt to warp and/or distort in drying and cooking.
Thus, the defects in the conventional process hitherto used including using laminated woods are as follows:
1. It doubles time, labor, and cost, as it requires an extra drying step prior to gluing, and cooking prior to slicing or lathing.
2. It is apt to distort the wood due to drying and cooking, and will consequently lower the yield.
3. It requires a long cooking time (for example, 3 days at 80.degree.-100.degree.C), and it therefore requires a waterproof adhesive.
4. The use of resorcinol resin as a suitable waterproof adhesive results in leaving stains on the wood and distorts the wood.
5. It is impossible to use side and core parts of the wood, waste wood such as small timber, scrap timber and small diameter woods as raw logs.
Prior to the present invention, the inventor herein made various trials and experiments to find an improved method relating to mass-producing sliced veneers of wide area and making use of available lumber, taking into account the aforementioned defects of known processes.
As an example of the inventor's trials and experiments, original lumber or scrap timber was divided into a plurality or small rectangular solids or small flitches and joined together to form a laminated or composite flitch with waterproof adhesive after drying. The laminated flitch was next cooked so that it had a moisture content more than the fiber saturation point (hereafter called the f.s.p.) and then used in this trial. Swelling or shrinking also occurs within lumber as the moisture content therein changes to less than the f.s.p. Additionally, since the degree of this phenomena depends among other things upon the direction of the flitch relative to the axis of the wood, difficulty as regards warp and distortion occured in the finished veneer on account of the inner stress arising in the joined parts.
Therefore, the advent of such process in the production of veneer as omitting extra drying and cooking of wood has been a dream to those skilled in the field of wood production. Such process carried out without drying and cooking of wood might have saved a great deal of labor and fuel, prevented the product from distortion caused by drying and cooking of wood, and consequently resulted in a great increase in the yield. However, such a process has not been available, as in which (1) wood is properly glued in the presence of moisture, (2) a suitable adhesive is employed, which cures to glue the flitches and sheets of veneer in the presence of moisture, and (3) the adhering surfaces of flitches larger in width and thickness are properly smoothed.
The present invention is outstanding in overcoming the above difficulties. Specifically, the present invention is concerned with a process for the production of sheets of veneer, which is characterized by the feature in that the entire process is carried out at the moisture content of the wood at or above the f.s.p. and which process comprises sawing or slicing a log into individual flitches, smoothing and gluing with adhesive to form a composite or laminated flitch, and slicing the composite flitch into sheets of veneer in various desired widths which can be glued to a substrate or a veneer in a single operational step.
That is a new process has been devised in the form of an improved veneer with consideration being given to the fact that with a moisture content at or above the f.s.p., lumber does not undergo the aforementioned phenomena of swelling or shrinking due to changes in the amount of the moisture content. In the improved process, according to the present invention, the flitches have no difficulties as mentioned above as regards to whether they are dry or moist. Thus, no inner stress is generated or produced at the joined parts between the flitches, so that no distortion, warp, or splitting will occur in the veneers sliced from the composite flitch according to the present invention.
Carrying out all the steps at the moisture content at or above the f.s.p. makes the following possible:
1. It makes the step of smoothing easy and effective before gluing and that it is necessary to conduct that step at such an elevated moisture content.
2. It suppresses the occurrence of the inner stress which would be frequently produced after the step of gluing. If one or two steps of those processes are conducted at the moisture content below the f.s.p., change of the wood size takes place due to the differences of the kinds of wood, growing circumstance, and anisotropy, which afterwards causes them to warp by producing inner stress.
3. It makes them maintain the smoothness of the smoothed surface which is the most important condition for the step of gluing.
Then, the reason for the importance of such step as smoothing and close adhering for gluing or joining can be described as follows:
1. Otherwise, when the veneer for fancy board comes to be prepared, it is liable to produce gaps at the joining line into which invasion of the adhesive occurs and makes them soiled.
2. When a coating of paint, varnish, or resin is made after some sheets of veneer are glued to the substrate, it is liable to foam at the gap of the joining line, and makes them inmiscible with each other which prevents the close adherence of the paint, varnish or resin on to the veneer.
Furthermore, by making use of the aforementioned concept according to the present invention, any sheets of veneer or wide or large area can be made and overlaid over a substrate by a single operational step to form a fancy board having desirable patterns of wood grain and inconspicuous joint lines. Of course veneers of narrow area may also be produced as desired.
Still furthermore, by carrying out the process in accordance with this invention, any sheets of wide veneer having every sort and kind of pattern of grain, and evenness of such physical properties as the rate of shrinkage and the degree of splitting on overall the veneer can be available.
Therefore, a general object of the present invention is to provide a process for industrially mass-producing sliced veneer sheets having desirable patterns and inconspicuous joint-lines in large quantities and in which the veneer have a wide area large enough to cover over an entire substrate in a single operational step without troublesome mending or patching as was required in conventional gluing of sliced veneers.
Another object of the present invention is to provide a process for industrially mass-producing sliced veneers to be glued over an entire substrate in large quantities and in which the veneer is provided with desirable technological and esthetic patterns, for example checker patterns, mosaic patterns, compound patterns and so on formed by a combination of the flitches having various grain patterns of the wood.
A further object of the present invention is to provide a process for industrially mass-producing sliced veneers to be glued over an entire substrate in one operational step thereby reducing the amount of labor required.
Still another object of the present invention is to provide a process for industrially mass-producing a fancy board in a single operational step by gluing a sheet of sliced veneer or wide area onto a substrate, and without having to place in order a plurality of small sliced veneers on the substrate one by one as was required heretofore.
A still further object of the present invention is to introduce a process for the production of veneer, which is carried out efficiently without drying and cooking, and in which the fuel and electric power expenses are saved because of no drying and cooking steps required.
Still another object of the present invention is to introduce the process which is carried out at moisture contents at or above the f.s.p., so as to prevent distortion or warp of the wood, and consequently to bring a high yield of sliced veneer from a raw log.
A still further object of the present invention is to provide a industrially mass-producing process in which larger flitches, 100-500mm or more in thickness can be smoothed on their adhering surfaces in one operational step which have not been able to be smoothed according to the conventional process.
Still another object of the present invention is to provide a process for industrially mass-producing wide sliced veneer sheets in which waste timber, small diameter wood, as well as side and core parts of the woods which have been impossible to be utilized for such purpose are made full use of according to this invention.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described in relationship to specific embodiments, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope of equivalents of the claims.